Although it is well appreciated that the physical basis of cell electric excitability is the voltage-dependent permeability of the cell membrane, the molecular mechanisms for this process are not completely understood. The overall objective of the present proposal is the understanding of the alamethicin-induced voltage-dependent conductance in planar lipid bilayer membranes at the molecular level. To this end, we propose studies that involve chemical modification of the pore-forming molecule and subsequent testing of those alamethicin analogs in well-defined lipid bilayers with respect to their abilities to induce a voltage-dependent conductance. These chemical alterations may affect the conductance properties of the alamethicin molecule and thus reveal important correlations between structure and function. Alamethicin is well suited for this purpose since its structure has been well characterized. Using a combination of chemical and photochemical techniques, as well as lipid bilayer studies, we will investigate the mechanisms that determine the gating properties and the structure of this ionic channel. On the basis of the alamethicin structure and on current models for the alamethicin channel gating and formation, we plan to synthesize phospholipid-alamethicin conjugates, a cholesterol-alamethicin conjugate, and alamethicin dimers. The phospholipid-alamethicin conjugate will help to answer the question of whether insertion of monomers lying at the membrane surface due to the applied potential is a necessary step in channel gating. Alamethicin dimers will be important in the study of the process of alamethicin aggregation in the membrane. Finally, the cholesterol-alamethicin conjugate will be useful in the understanding of the mechanisms by which this lipid modulates the alamethicin-induced voltage-dependent conductance. We think that even limited understanding of voltage-induced pore formation in simple systems will pave the way towards the understanding of similar processes in nerve and muscle.